Stoker control



March 94 E. K. scoem STOKER CONTROL Filed Feb. 24, 1936 2 Sheets-Sheet 1 r o p w @m 9m RN ow mtm Smfl fi I; 5 NM Mm 33 vN mm MN .mm. hm v .n\ \N m mum Mm MN fl I 4% e mN Q N March 11,1941" E. K. SCOGGIN 2,234.388

STOKER CONTROL Filed Feb. 24, 1936 2 Sheets-Sheet l I $9.3

Ill //3 fvvmz or Elmer )5. 60099172 Patented Mar. 11, 1941 UNITED STATES PATENT OFFICE STOKER CONTROL Application February 24, 1936, Serial No. 65,226

32 Claims.

This invention relates to controls, and more particularly to a type of control adapted to regulate feeding of fuel to a fire under predetermined temperature conditions and/or at predetermined time intervals.

One object of this invention is the provision of an improved control system arranged to operate a mechanism, such as an automatic stoker, upon a predetermined fall in temperature to control the said temperature in a space to be heated, or at predetermined time intervals in the absence of such a temperature drop, in order to maintain combustion of the fire at all times.

Another object is the provision of a system which will automatically preclude the operation of a stoker under the control of a timed mechanism during, and for an appreciable interval after, operation of the stoker by a temperature responsive mechanism, such as a conventional thermostat.

A further object is the provision of a system wherein continued operation of a stoker by temperature controlled means after energization by timed mechanism is precluded in the absence of a call for heat in the space to be heated.

Still another object is the provision of improved mechanism for controlling intermittent timed feeding of fuel to a source of combustion.

A further object is the provision of suitable mechanism to vary the duration of a period during which fuel is fed to a fire under the control of timed mechanism.

A still further object is the provision of means to vary the interval between the timed operations of a timed fuel feeding control mechanism.

A morespecific object is the provision of improved mechanism to accomplish the above and other objects, which will be durable in construction and reliable in operation.

A further specific object is the provision in a system including a thermostat and a timer mechanism, of an auxiliary temperature responsive circuit controlling mechanism in the thermostat circuit.

Other objects will in part be obvious and in part be pointed out hereinafter.

Accordingly, the invention consists in the arrangements of parts, combinations of elements and features of construction, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, wherein is shown one of the various possible embodiments of this invention;

Figure 1 is a schematic view showing certain parts of the structure of the instant invention and a diagrammatic representation of one form of control circuit;

Figure 2 is an enlarged sectional elevation 5 taken substantially along line 22 of Figure 1;

Figures 3, 4 and 5 are detailed views of certain portions of the structure shown in Figure 1, showing certain movable parts in different positions; 10

Figure 6 is a detailed view showing another portion of the structure in a different position, and

Figure 7 is a sectional view taken along line r 1 1 of Figure 6.

Similar reference characters refer to similar parts throughout the several views of the drawings.

Referring now to the drawings and more particularly to Figure 1: a suitable motor, gen- 20 erally indicated at l0, which may serve to drive any suitable apparatus such, for example, as an automatic stoker (not shown), to feed fuel to a furnace, is controlled, in a manner to be hereinafter described, by the conjoint action of a 5 suitable thermostat, schematically indicated at H, and a timer mechanism, generally indicated at l2. Timer mechanism I2 is so constructed and arranged as to operate motor lil for a predetermined period at suitable intervals, such as,

illustratively, four minutes every half hour, such periods and intervals being subject to variation at the will of the operator. Provision is also made to render timer mechanism 12 ineffective when motor i0 is in operation under the con- 5 trol of thermostat II during the normal operatin period of timer mechanism I2 and for a suitable period subsequent to the cessation of such operation. One system and arrangement of parts adapted to accomplish the above and other results will now be described.

Timer mechanism I 2 includes a suitable motor l3 which may be of the synchronous type, having a field winding M to which current is supplied through lead wires i5 and I6 from suitable line wires I1 and [8, which in turn lead to a suitable source of electrical energy (not shown). A pair of cams l9 and 20 are coaxially mounted, in a manner to be hereinafter described, on a sleeve 22 and rotated in a counter-clockwise direction as indicated by the arrow inFigure 1, through suitable gearing and friction mechanism, also to be described hereinafter, by motor l3. Cam I9 is preferably constructed in such a manner as to have two oppositely disposed low surfaces 19a with intervening high surfaces I91). A suitable projection |9c is also formed on the face of cam I9. An elongated aperture |9d having a projection in the form of a pointer |9e on its inner periphery, is cut into cam I9, and a slot |9j is also cut through cam l9 at a point spaced away from aperture [911.

Cam has two oppositely spaced high surfaces 2||a of a peripheral extent slightly less than the peripheral extent of low surfaces I90. Suitable indicia 2017 may be suitably affixed to or imprinted on a portion of the surface of cam 20. A stud 2| having a threaded end is provided for engagement with a suitable aperture in cam 20.

By reference to Figures 1 and 2 of the drawings,

it will be seen that when the parts are in assembled relation stud 2| is passed through slot |9f and threadedly engaged with cam 20, and indicia 29b is positioned below and adjacent aperture |9d in alignment with pointer |9e. By loosening stud 2| cam 20 may be rotated about sleeve 22 with respect to cam I9 and the composite high surface area of cams l9 and 20, which includes the total of the high surface areas I9?) and 20a, may be varied. Indicia 20b will be correspondingly varied with respect to pointer |9e and accordingly may indicate, in the form of time indications, as will be explained hereinafter, the combined low surface area of cams l9 and 20.

Having particular reference to Figure 2, it will be seen that motor |3 has a drive shaft 23 to which is afiixed a suitable pinion 24 which engages a reduction gear 25. Pinion 24 is driven through a suitable conventional reduction train (not shown). Gear 25 has an axle 26 journaled for rotation in a sleeve 26a secured to a mounting bracket 21. Mounting bracket 2! may be secured in any suitable manner, as by screws 28, to an insulating panel 29 which may comprise a portion of a suitable casing (not shown). Axle 26 carries at one end a second reduction gear '30 which engages a driven gear 3| which is mounted on sleeve 22. Gear 3| may have a diameter substantially equal to that of gear 25 in order that sleeve 22 and shaft 23 may be in substantial alignment. A suitable friction disc 32, which may be of any desired material but for which, in prac-- tice,cork has been found advantageous, is mounted on sleeve 22 adjacent gear 3|. Cams 20 and I9 respectively are then superimposed on disc 32. A stud member 33, suitably mounted in panel 29, passes through the interior of sleeve 22 and serves as an axle for rotation of sleeve 22 thereabout. Sleeve 22 has a flanged annulus 22a for abutment with a rim 33a of stud 33. A housing 34 holds a spring '35, positioned about the exterior periphery of sleeve 22, in close juxtaposition with the exterior face of cam 9. A washer 36 may be superimposed over the outer end of housing 34 and held in place by the coaction of a spring collar 3! with a suitable groove 33b adjacent the outer end of axle 33.

It will now be seen that rotation of shaft 23 is imparted to cams l9 and 29 through sleeve 22 and the chain of reduction gears 24, 25, and In practice it has been found desirable to arrange the gearing ratio in such manner that cams I 9 and 20 make one complete rotation every hour. Y

It will further be seen that friction disc 32 provides means whereby cams I9 and 20 may be rotated with respect to sleeve 22 for any desired purpose, such as adjustment of the timer mechanism above described.

A cam follower assembly, generally indicated at 40, is pivotally mounted adjacent a portion of the exterior periphery of cams l9 and 20. Cam follower 40 is comprised of a block 43 of suitable insulating material on which are mounted by anysuitable means, such as screws 44, a plurality, illustratively three, of spring contact arms 45, 46

and 41, the purpose of which will be described hereinafter.

It will now be seen that the cam assembly comprised of cams l9 and 20 rotates adjacent cam follower 49 and presents thereto at spaced intervals a low surface |9a of cam 9. The area of surface |9a is determined by the relative position of an adjacent high surface, 29a of cam 20. Variation of the position of high surface 29a with respect to low surface |9a correspondingly varies the position of indicia 292) with respect to pointer I96. Since the cam assembly rotates once an hour each low surface |9a, except under circumstances to be hereinafter described, is juxtaposed to cam follower 49 for a period of minutes during each hour. brated to designate minutes and the position of pointer |9e with respect thereto accordingly indicates the number of minutes during each hour that each of low surfaces |9a is juxtaposed to cam follower 40.

The mounting of cam follower 49 may comprise a mounting member 4| to which block 43 may be secured by any suitable means, such as screws 42. Mounting member 4| may be pivotally mounted on panel 29 through pivot 49, and secured, as by a spring collar 50. A spring 5| secured to an arm 4|a extending from mounting member 4|, and a fixed point on panel 29, such as screw 28, (see Figure 2), is so desig ed and positioned as normally to hold block '43 adjacent the periphery of cams l9 and 20. A downwardly depending lug 48 having a cam surface 48a and a latching surface 48b, for a purpose to be herein-,

after described, is also afiixed to mounting member 4| and may comprise an integral pant thereof.

It will now be seen that the timed rotation of cams I9 and 20 causes cam follower 40 to drop a distance equal to the difierence between high surface 1 9b and low surface I911, due to the combined force of gravity and spring 5| each time a low surface area of the cam assembly rotates into engagement with block 43, and that cam follower 40 is held in a raised position for the period during which the high surface |9b of cam I9 is adjacent thereto. The fall of cam follower 40 'to its low position causes the closure of a circuit in a manner and for a purpose to be hereinafter described, while a subsequent rise of cam follower 49 by juxtaposition to high surface |9b of cam |9 causes the circuit to re-open.

While in the preceding discussion cam l9 has been pointed out as having a pair of oppositely disposed low surfaces in order to permit a drop of cam follower 40 at every half rotation of cam |9 by motor l4, provision is made whereby such a drop may occur only once during every full rotation of cam IS. The mechanism for accomplishing this comprises a segment 55, one surface 55a of which is comprised of an are having a radius of curvature substantially equal to high surface |9b of cam l9, and the other surface 55b of which is comprised of an are having a radius of curvature equal to low surface l9a of cam 9. A projection 55c.formed on surface 55b is substantially equal in contour and dimensions to projection |9c on cam [9. -A securing screw 56 passing through an aperture in segment 55 may e Indicia 20b, therefore, may be caligage a suitable threaded opening in cam I9 to hold segment 55 in related assembly with cam I9. Additional securing means to prevent rotation of segment 55 about screw 56 may be provided in the form of an aperture 55d in member 55 and a suitable projection I9g on the surface of cam I9 adapted to engage therewith (see Figure 7) From the above it will be seen that the portion of the peripheral configuration of the cam assembly adjacent segment 55 may be varied by a simple reversal of segment 55 to the position shown in Figure 6 by release of screw 56. It will also be seen that when'segment 55 is in the posi tion shown in Figures 1, 3, 4 and 5 of the drawings both low surfaces I9a of cam I9 will be juxtaposed to cam follower 40, but that when the position of segment 55 is reversed, as in Figure 6, that portion of the cam assembly adjacent segment 55 will present an unbroken high surface area. Accordingly, when segment 55 is in the position shown in Figures 1, 3, 4 and 5 of the drawings cam follower 40 will drop twice during each full, or iilustratively, hourly, rotation of the cam assembly comprising cams I9 and 20 and segment 55, to close a circuit and actuate stoker motor I0, as will be hereinafter set forth, But when segment 55 is reversed in the position shown in Figure 6, such actuation will occur only once during each hour.

As shown in Figures 1, 3, 4 and 5, in dotted lines a lever 60 is pivotally mounted as by means of a pivot 6| on, and to the rear of, operating panel 29. A projection 60a extends forwardly from lever 60 through a suitable aperture 29a. in panel 29 immediately adjacent lug 48, and a second projection 60b extends from lever 60 through an aperture 29b at a second point spaced from aperture 29a. Projections 60a and 60b are adapted to be moved in a manner and for a purpose set forth hereinafter, and apertures 29a and 29b serve not only to permit passage of projections 60a and 60b through panel 29, but also as stops to limit the movement thereof. A suitable extension, which comprises a weight 600, extends beyond pivot' point 6I of lever 60 and serves normally to hold lever 60 at the extreme limit of pivotal rotation in a clockwise direction, such limit, as above stated, being defined by engagement of projection 29a and 2912 with the right hand (as seen in the drawings) walls of their associated apertures 60a and 601) respectively. A pivoted spring arm 62' is mounted adjacent projection 60b and is adapted to be actuated in a manner to be hereinafter described toward and away from projection 60b.

The fall of insulating block 43 upon engagement with low surface I9a of the cam assembly, as above stated, closes a circuit in a manner hereinafter described, which serves to draw arm 62 to the left as viewed in the drawings. likewise, the closing of a circuit by thermostat II in a manner to be described hereinafter also draws spring arm 62 to the left as shown in Figure 1.

Referring now particularly to Figure 3, insulating block 43 is shown in engagement with the low surface 19a of cam I9. The circuit is now closed by means of cam follower 40 and spring arm 62 is shown as bearing to the left against projection 60b of lever 60. overcomes the gravitational pull of weight 600 and causes projection 60a to' abut the inner surface of lug 48. Upon continued rotation of the cam assembly engagement of high surface I9b with insulating block 49 will cause cam follower 40 to rise and break the circuit, which will in turn release the pressure of arm 60 against projection The pressure of spring arm 62 60b and permit the parts, with the exception of the continuously rotating cam assembly, to return to the position as shown in Figure 1.

Should spring arm 62, however, be actuated by thermostat II while insulating block 43 is in engagement with a high surface portion I9b of cam I9, spring arm 62 will engage projection 60?) and force projection 60a into engagement with cam surface 48a and therealong into engagement with latching surface 49b. Upon release of the pressure of arm 62 the parts will remain in the position as indicated in Figure 4, with projection 60a engaging latching surface 48b even after low surface I9a has rotated to a position adjacent insulating block 43, until continued rotation brings the parts into the position shown in Figure 5, whereupon projection I9c raises insulating block 43 and hence cam follower 40 to a height sufficient to release projection 60a from engagement with latching surface 48b of lug 48. Thereupon weight 600 turns lever 60 about its pivot 6| until projection 60a. again abuts the righthand wall of aperture 29a.

It is to be noted that projection I90 is adjacent an end of low surface I9a in a direction counter to the direction of rotation of the cam assembly. Accordingly, it will be seen that if cam follower 40 and lug 48 are in such position as shown in Figure 4 as to necessitate release from engagement with projection 60a by action of projection I90, it will be impossible to close the circuit associated with cam follower 40 for a definite period, subsequent to the release of projection 60a from engagement with latch member 48b. This period is of a duration suflicient to permit an entire high surface I92; to pass cam follower 40 before the presentation of a low surface I9a to permit cam follower 40 to drop.

It may here be pointed out that with the parts, including segment 55, in the position as shown in Figures 1, 3, 4 and 5 of the drawings, projection 55c serves the same purpose and acts in the same manner as projection I 90.

Having particular reference to the wiring diagram shown in connection with Figure 1, line wires I! and I8 lead through the primary Ia of a suitable step-down transformer I00. A wire IOI leads from one side of the secondary I00b of transformer I00 to a coil mm of a relay, generally indicated at I02. Relay I02 includes contact arms I03, I04, I and is also operably associated with spring arm 62. In practical form spring arm 62 may comprise an extension of one of the arms I03, I04 or I05 of relay I02. A wire 9'! leads from the side of relay coil I02a opposite wire IOI to a junction 98 from which a wire 99 leads to arm I03. A Wire 96 leads from junction 98 to a junction I06 from which extends a wire I01 to a contact I08 which is adapted to engage opposite contact I08 carried by spring arm 41 of cam follower 40. A second wire I09 also leads from junction I06 to a contact IIO adapted to engage an associated contact H0 carried by bimetallic thermostat II. A wire III leads from. terminal I I2 of thermostat II to a contact II3 which is adapted to engage an opposed contact II 3' carried by spring arm 45 of cam follower 40. The arm 45 of cam follower 40 bears a contact H4 at an end thereof, adapted to engage a contact II4. A wire I I5 leads from contact II4 to a a wire II'I leads to transformer secondary I00b at the side opposite wire IOI. A second wire II 8 leads from junction II6 to a mercury switch H9 associated with a thermostatic element I junction II 6, from which for a purpose to be more fully described hereinafter, and a second wire I2I leads from mercury switch IIS to a contact I22 positioned adjacent a corresponding contact I 22' carried by a movable arm of thermostat II.

Arm I03 of relay 602 is adapted under circumstances to be hereinafter described, to engage a contact I23. A wire I24leads from contact I23 to a terminal I25 carried by cam follower 40. Terminal I25 may, in -practice, comprise one of holding screws 44, provided electrical contact is established therethrough with arms 45, 46 and 41 and hence contacts H3, H4 and I08. Arms I04 and I05 are adapted to engage respectively contacts I25 and I21 which in turn are connected with wires I28 and I29 respectively,- leading from line wires I7 and I8. The opposite ends of arms I04 and I05 are connected through wires I30 and I3I respectively to motor I0. Accordingly, it will be seen that energization'of relay I02 in a manner to be explained hereinafter, will cause arms I04 and I05 I to engage contacts I25 and I2! respectively and 'tablished' from transformer secondary operate motor I directly from line 'wires II and I8.

Assuming now that the parts are in the position shown in Figure 1, it will be seen that no circuit is closed through relay coil I02@ and in consequence arms I03, I04 and I are open and spring arm 62 exerts no pressure on projection 0017.

Now, having particular reference to the circuit controlled by timer mechanism I2, assume that the cam assembly comprised of cams I9 and 20 has rotated to the position shown in Figure 3.

-Insulating block 43 willdrop, permitting contacts H4 and I00 to engage respectively contacts II4 and'I08. An energizing circuit is now established from transformer secondary I00b through wire IOI, relay coil I021, wire 01, junction 98, wires 96 and I01, contacts I08I03, arms 41 and 46, contacts II4'-II4, wire' II5, junction H6, and wire III back to transformer secondary I00b, which serves to energize relay I02. Arm I03 is now pulled inwardly to engage contact I23, whereupon a holding circuit is es- I00b through wire IOI, relay coil I02a, wire 91, junction 98 as above described, and thence through wire 99, arm I03, contact I23, wire I24, terminal I25, arm 46, contact 4' to contact H4- 4', wire II5, junction H6 and wire III to transformer secondary I00b, wires 96 and I0! and contact I08, I08 being shunted out. Simultaneously, wih the closing of arm I03, arms I04 and I05 engage contacts I26 and I21 and stoker motor I0 is placed in operation. Likewise, simultaneously spring arm 62 bears against projection 50b and forces projection 60a into engagement with the right-hand surface of lug 43, as shown in Figure 3. Upon further rotation of the cam, assembly a high surface I917 raises insulating block 43 and breaks, first, con-, tacts I00I08' and in a relatively short time thereafter contacts Il4-I I4. It will be seen from the description of the circuit above given that motor I0 continues to operate until contacts I I4II4' are broken and in the absence of any activity on the part of thermostat II, still assuming it to be in the open position shown in Figure l, the circuit through relay coil I0-2a is broken to permit arms I03, I04 and I05 to move away from their respective contacts and likewi'seto permit spring arm 52 to release its pressure on projection 30b. In t '2 continued absence of activity on the part of thermostat II this cycle will be continued at hourly or halfhourly intervals, depending upon the position of segment 55, and such actuation of motor I0 will be for a period to be determined by the relationship of cams I9 and 20 with respect to each other.

Assume now, with reference to the circuit controlled by thermostat II, the parts, including the timer mechanism I2, being in the position shown in Figure 1, that there is a call for heat in the space, the temperature of which is adapted to be controlled by thermostat II. Contacts I22--I22 close and after an interval and upon a further drop in temperature contacts IIOIIO' close. The purpose of this plurality of contacts will be described hereinafter. A circuit ,is now established through contact I 22, wire I2I, mercury switch II3, assuming switch H9 is closed, which it will be except under certain conditions to be hereinafter set forth, wire II8, wire II'I, transformer secondary I00b, wire IOI, relay coil I02a, wires 01, 96 and I09, contacts IIO-I I0, thermostat II and contact I22. This circuit serves also to energize relay coil I02a and close its associated contacts to establish a holding circuit from transformer I00 through wire IOI, relay coil I02a, wire 01, junction 98, wire 09, arm I03, contact I23, wire I24, terminal I25, arm 45, contacts II3--I I3, wire III, terminal II2, thermostat I2, contacts I22I22', wire I2I, mercury switch 9,

wire II8, junction IIB, wire III back to trans-- former secondary I00b. Contacts IIOI I0" and wires I09, I06 and 96 are shunted out. Spring arm 62 is likewise actuated causing projection 60a to be pulled into latching engagement with latching surface 48b of lug 48. Simultaneously stoker motor I0 is put in operation. It will now be seen'that upon continued rotation of cam III to the position as shown in Figure 4, wherein it presents a low surface I9a. to cam follower 40,

projection 60a serves to hold cam follower 40 through latching surface 48b in the same position asthough it engaged a high surface, and accordingly will not permit closing of the circuit through contacts I I4-II4', and I08-I08' as previously discussed.

If, however, during the time low surface area I3a is adjacent cam follower and the requirement for heat in the space to be heated has been satisfied, relay I02 is deenergized and pressure on the spring arm 62 correspondingly released, whereupon the engagement of projection I90 or projection 550, as thecase may be, with insulating block 43 will serve to lift lug 48 out of latching engagement with projection 60a and permit the same to return to the position shown in Figures 1 and 5 under the impetus of weight 60c.

The system is now in condition-for operation by the timer mechanism upon the next presentation of a low surface I00, to cam follower 40.

If, however, during the period immediately following release by one of the projections I90 or 55c, thermostat II again responds to a call the room thermostat makes frequent and/or prolonged calls for heat, the timer mechanism may rotate for an indefinite period without actuating the stoker, but that under other conditions, such as an unusually warm spell of weather, the timer mechanism will serve to maintain a fire in the furnace even though no demand for heat whatsoever is made by thermostat II. It will further be seen that the timer mechanism is rendered incapable of operating the stoker during actuation by the thermostat II and for a period subsequent thereto. Such a period may vary from, at a minimum, approximately a half an hour, assuming that thermostat II satisfies the call for heat in the space to be heated immediately prior to the passage of a projection I 90 or 550 past cam follower to a period of nearly two hours, assuming that cam segment 55 is in its reversed position as shown in Figure 6 and that the thermostat satisfies the call for heat in the space to be heated immediately subsequent to the passage of projection I90 past cam follower 40.

Referring back to thermostat I I, it has been found desirable to arrange the contacts I I0 and I22 in such manner that they will engage their opposite contacts H0 and I22 respectively at different temperatures, as for example, contact I22-I22 may make at 72 and contact I I0I I0 at 70. This temperature may of course be adjusted to the individual heating requirements of the space to be heated. Assume that the temperature falls below 70. Both contacts I I0-I l0 and I22I22 make to close the energizing circuit above described and energize relay I02. 'Upon such energization arm I03 will engage contact I23. The maintaining circuit above described is now established and stoker motor I0 continues to operate. Now assume the tempera- 1 ture rises to 71. Contact IIO-IIO' is broken but stoker motor I0 continues to operate since relay I02 is closed through the maintaining circuit above described. Upon a temperature rise above 72, however, contacts I22I22' break,

40]relay I 02 is deenergized, and stoker motor I0 ceases to operate. Now assume that the temperature falls from 72 to 71. Contact I22I22 makes but stoker motor I0 is not started since no circuit is established. However, if the timer (5, mechanism I2 at this point energizes relay I 02 through the closing of contacts II4II4' and contacts I08-I08 and actuates the stoker motor I0 for the predetermined period, it will be seen that contact II3-I I3 is open and that at the end of the time period the circuit is broken by the opening of contacts II-I-I I4 and I08--I08 prior to the making of contact II 3-I I3.

The inclusion of contact II3I I3 in the circuit thus serves to maintain the temperature of the space to be heated within the normal range of thermostat II since, in the absence of such circuit breaking means, and assuming contact I23 to be directly connected to wire III, if relay I02 and motor I0 were energized by timer mechanism I2 with the room temperature at 71 and therefore with contacts IIO--.I I0 and I22-I22 open and closed respectively, stoker motor I0 would continue to operate through a holdingcircuit comprising transformer secondary I00b, wire IOI, relay coil I02a, wires 97 and 98, arm I03, contact I23, wire III, terminal II2, thermostat II, contact I22I22', wire I2I, switch H9 and wires H8 and H1, after the termination of the timed period until the temperature reached 72 to break contact I22I22'.

The room temperature may, therefore, through the operation of contact II3-I'I3 above described, be maintained constantly within the normal predetermined differential of the thermostat as, in the illustrative example above given, between 70 and 72.

It will now be seen that the provision of contact II3-II3 serves to preclude actuation of stoker motor I0 by thermostat II while timer mechanism I2 is. in control, and further that no circuit originally energized by timer mechanism I2 may be held through thermostat I I after the termination of a timed operating period in the absence of a call for heat serving to close both contacts I10IIO and I22I22.

In some instances, however, it may be desirable that the temperature be maintained constantly above the normal differential of thermostat II or above the making point of contacts IIO-IIO', as in the illustration above, 72. In this case contact II3II3 and its associated arm 45 and wiring may be omitted and wire I II connected directly to contact I23. Then, in the event of a temperature fall to 71 and consequent making of contact I22I22', contact IIO-IIO' remaining open, if the stoker is started and relay I02 energized by the above described action of timer mechanism I2, upon the termination of the timed period of operation, stoker motor I0 will continue in operation through a holding circuit comprising transformer I00, wire I M relay I02, wires 91 and 09, arm I03, contact I23, wire II I, terminal 2, thermostat II, wire 12I, mercury switch H9 and wires H8 and II! back to transformer I00, until the temperature reaches 72 and contact I22-I22 breaks. It will accordingly be seen that While contact H3 and its associated wiring forms a desirable adjunct to the system as a whole, it may be omitted if the operation above described is desired.

Referring now to thermostatic element I20 associated with mercury switch II 9, it has been found desirable in many instances to position a suitable high limit control adjacent, say, the water boiler of a heating system in order to preclude an unnecessary rise in th temperature of. water during such a transition period as, for example, from a night temperature of approximately 60 to a day temperature of approximately 70. tion period in the absence of such a control as indicated diagrammatically by thermo-responsive element I20 and mercury switch IIS, the temperature of the water in the boiler may rise to an unnecessarily high degree due to the prolonged action of the stoker in raising the temperature to normal day heat. Such a high limit control suitably interposed in the thermostat circuit serves to cut off the stoker for sufficient periods to permit cooling of the water to normal operating temperatures even though the position of thermostat II still indicates a low temperature in the space to be heated. This high limit control serves, therefore, to retard continuous action of the stoker in such a manner as to prevent unnecessary overheating of the boiler.

The inclusion of the above described control is particularly advantageous in mild climates where the temp :rature increases very rapidly with the It has been found that during such transiris of the sun. During the night the tempera- I perature would rise due to the aforementioned demand for heat, to a point suflicient to overheat the building and, under normal circumstances, a considerable time would elapse before the temperature could cool to the desired level. The inclusion of the limit control therefore serves priymarily to preclude too rapid a rise in boiler temperature in order to compensate for a relatively rapid rise in outdoor temperature, and prevents overheating of the space to be heated due to the combined effects of the outdoor temperature and heating system.

A second high limit control generally indicated at I32, which may comprise a suitable stack switch, diagrammatically indicated .by mercury switch I33 and thermostatic element I34, is interposed in the line circuit in order to provide an absolute cut-off should the temperature in the stack of the furnace, or, in other words, the combustion temperature, reach a point of danger.

It may here be pointed out that in the preferred embodiment of the invention motor I3 is connected through wires l5 and IE to line wires I1 and 18 between the high limit control I32 and the source of power supply, in order that the timed rotation of thecam assembly may be unaffected by the opening of mercury switch 133.

From the foregoing it will be seen that there is herein provided a system and a specific structure which embody the features of this invention and achieve the objects thereof including advantages of great practical importance.

As many possible embodimentsmay be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a control system, in combination, a circuit, condition responsive means to open and close said circuit, additional means to open and close said circuit at predetermined time intervals, and a mechanical latch means movable by said condition responsive means to latching position to maintain said additional means in open position during the period when said condition responsive means closes said circuit and for an appreciable period subsequent to the opening thereof by said condition responsive means.

2. A circuit controlling mechanism, comprising, in combination, a relay, temperature responsive means to open and close a circuit through said relay, time controlled means to open and close a circuit through said relay, and means to preclude closing of said time controlled circuit during the period when said circuit is closed by said temperature responsive means and immediately subsequent to reopening thereof, said last mentioned means comprising an arm associated with said relay and adapted upon closing of said relay to engage mechanically with said time controlled means.

ing, in combination, a relay, temperature responsive means to close a circuit through said relay, time controlled means to close a circuit through said relay, means to preclude closing of said time controlled circuit while said temperature controlled circuit is closed and for an appreciable period subsequent to opening thereof, said means comprising latch means associated with said relay and said time controlled means, and means on said time controlled means to release said latch means after the termination of said predetermined period.

5. A control system for stokers, including a plurality of circuits, closure of either of said circuits adapted to operate said stoker, condition responsive means including a switch to close one of said circuits, time controlled means including a switch to close another of said circuits, means actuated by the closure of one of said switches to maintain another of said switches open during closure of and for a variable period subsequent to reopening of said one of said switches, said means comprising mechanical latch means actuated by the closure of one of said switches to age the other of said switches to hold the same in open position, and means actuated by cam means having high and low surfaces and pivotally mounted cam follower means, the arrangement being such that engagement of said cam follower means with one of said surfaces upon rotation of said cam means energizes said relay, and means actuated by said first mentioned means to preclude pivotal movement of said cam follower means.

7. A device of the character described, comprising, in combination, a relay, means to energize said relay, additional means to energize said relay, said additional means including rotatable cam means having high and low surfaces and pivotally mounted cam follower means, the arrangement being such that engagement of said cam follower means with one of said surfaces upon rotation of said cam means energizes said cam follower means with one of said surfaces' upon rotation of said cam'means energizes said relay, means actuated by said first mentioned means to preclude pivotal movement of said cam follower means, said means including latch means associated with said cam follower means and means on said cam means to release said latch means.

9. A device of the character described, comprising, in combination, a relay, means to energize said relay, additional means to energize said relay, said additional means including rotatable cam means having high and low surfaces and pivotally mounted cam follower means, the arrangement being such that engagement of said cam follower means with one of said surfaces upon rotation of said cam means energizes said relay, means actuated by said first mentioned means to preclude pivotal movement of said cam follower means, said means including latch means associated with said cam follower means and means on said cam means to release said latch means, said last mentioned means including a projection extending a substantial distance above said high surface.

10. A device of the character described, comprising, in combination, a relay, means to energize said relay, additional means to energize said relay, said additional means including rotatable cam means having high and low surfaces and pivotally mounted cam follower means, the arrangement being such that engagement of said cam follower means with one of said surfaces upon rotation of said cam means energizes said relay, means actuated by said first mentioned means to preclude pivotal movement of said cam follower means, said means including latch means associated with said cam follower means, means on said cam means to release said latch means and means to return said latch means to unlatching position upon release by said means on said cam means.

11. A device of the character described, comprising, in combination, a circuit, means to close said circuit, additional means to close said circuit, said additional means including rotatable cam means having active and inactive surfaces and cam follower means adjacent thereto, the arrangement being such that engagement of said cam follower with said active surfaces closes said circuit, means to rotate said cam at a predetermined speed whereby said active surfaces engage said cam follower means at predetermined intervals, and means actuated by said first mentioned means to preclude closing of said circuit by said additional means.

12. In a control system in combination, a motor, condition responsive means to energize said motor through a circuit, time controlled means to energize said motor through another circuit, and means to prevent continued energization of said motor through either of said circuits after original energization through the other of said circuits in the absence of condition change sufficient to cause said condition responsive means to energize said motor.

13. In a control system in combination, a motor, condition responsive means to energize said motor through a circuit, time controlled means to energize said motor through another circuit and means to prevent continued energization of said motor through said first mentioned circuit after original energization by said second mentioned circuit in the absence of condition change sufiicient to cause said condition responsive means to assume motor energizing position.

, 14. In a control system in combination, a motor, condition responsive means to energize said' motor through a circuit, time controlled means to energize said motor through another circuit, means to prevent continued energization of said motor through said first mentioned circuit after energization by said second mentioned circuit when said first mentioned circuit is not closed through said condition responsive means, said means including a switch, and means associated with said time controlled means to open said switch prior to energization of said motor through said second mentioned circuit, and close said switch subsequent to deenergization of said motor therethrough.

15. A device of the character described, comprising in combination, motor actuating means, first means to energize said actuating means, second means to energize said actuating means, said second means including a revolvable cam having a high and a low surface and a pivoted cam follower adjacent thereto the arrangement being such that engagement of said cam follower with one of said surfaces energizes said actuating means, means to rotate continuously said cam at a predetermined speed whereby said one of said surfaces engages said cam follower 'at predetermined intervals to energize said actuating means at predetermined intervals and means actuated by said first means to preclude energization of said actuating means by said second means for an appreciable period subsequent to termination of energization of said actuating means by said first means.

16. A device of the character described, comprising in combination, motor actuating means, first means to energize said actuating means, second means to energize said actuating means, said second means including a revolvable cam having a high and a low surface and a pivoted cam follower adjacent thereto the arrangement being such that engagement of said cam follower with one of said surfaces energizes said actuating means, means to rotate said cam at a predetermined speed whereby said one of said surfaces engages said cam follower at predetermined intervals and means actuated by said first means to preclude energization of said actuating means by said additional means, said last mentioned means comprising a latch member movable by said first means into latching relation with said second means.

17. In a stoker control system, in combination, condition responsive means to operate said stoker, time controlled means to operate said stoker, said time controlled means including a rotatable cam and a cam follower, said cam follower being movable into and out of stoker operating position according to the cam surface adstoker, time controlled means to operate said stoker said time controlled means including a rotatable cam and a cam follower, said cam follower being movable into and out of stoker operating position according to the cam surface adjacent thereto, means to rotate said cam at a relatively constant speed whereby said cam follower operates said stoker at predetermined intervals and mechanical means controlled by said condition responsive means to preclude operation of said stoker by said time controlled means during, and for an appreciable period subsequent 70 to, operation of said stoker by said condition responsive means, said last mentioned means comprising a latch movable upon operation of said stoker by said condition responsive means to engage said time controlled means.

19. In a stoker control system, in combination, condition responsive means to operate said stoker, time controlled means to operate said stoker, said time controlled means including a rotatable cam and a cam follower, said cam follower being movable into and out of stoker operating position according to the cam surface adjacent thereto, means to rotate said cam at a relatively constant speed whereby said cam follower operates said stoker at predetermined intervals, and mechanical means controlled by said condition responsive means to preclude operation of said stoker by said time controlled means during and for an appreciable period subsequent to operation of said stoker by said condition responsive means, said last mentioned means comprising a latch movable upon operation of said stoker by said condition responsive means to engage said time controlled means, and trip means associated with said cam to release said latch means after a desired interval.

20. In a control system, a motor, a relay adapted to operate said motor, a thermostat adapted to energize said relay, time controlled mechanism also adapted to energize said relay, said mechanism comprising revolvable cam means, means to revolve said cam means at a relatively constant speed, cam follower means operated-by said cam means and means operated by said cam follower means to operate said relay upon operation of said cam follower means by said cam means, and means operated by said relay to prevent effective operation of said cam follower means by said cam means during energization of said relay by said thermostat.

21. In a stoker control system, in combination, condition responsive means to operate said stoker, time controlled means to operate said stoker said time controlled means including a rotatable cam and a cam follower, said cam follower being movable into and out of stoker operating position according to the cam surface adjacent thereto, means to rotate said cam at a. relatively constant speed whereby said cam follower operates said stoker at predetermined intervals and mechanical means controlled by said condition responsive means to preclude operation of said stoker by said time controlled means during, and for an appreciable period subsequent to, operation of said stoker by said condition responsive means, said last mentioned means comprising a latch movable upon operation of said stoker by said condition responsive means to engage the cam follower of said time controlled means, said last mentioned means comprising an arm and a lever adjacent said cam means, the

arrangement being such that .said arm upon movement of said relay engages said lever and through said lever holds said cam follower means.

22.'A circuit-controlling mechanism, comprising, in combination, a relay, a temperature responsive means to open and close a circuit through said relay, time controlled means to, open and close'a circuit through said relay, said time controlled means comprising, in combination, cam means, cam follower means operated by said cam means, means to rotate continuously said cam means at a predetermined speed whereby said cam follower means is operated at predetermined time intervals and circuit controlling means operated by said cam follower means to close said circuit at predetermined time intervals, and means associated with said temperature responsive means to prevent effective operation of relatively constant speed, cam follower means operated by said cam means and means operated by said cam follower means to operate said relay upon operation of said cam follower means by said cam means, and means operated by said relay to prevent effective operation of said cam follower means by said cam means duringenergization of said relay by-said thermostat, and to maintain'said cam follower means inoperative for an appreciable period subsequent to opening of said circuit by said temperature responsive means.

24. In a control system, the combination of, a motor, means including a first circuit in control of said motor, control means for closing the first circuit to cause operation of said motor, a sec-, ond circuit in control of said motor, periodically operated control means for periodically closing the second circuit to cause periodic operation of said motor including continuously operated cam means and means controlled by the means including the first circuit and operated by closure of the first circuit to preclude closing of the second circuit for an appreciable period subsequent to opening of said first circuit. r

25. In a control system, the combination of, a motor, a first circuit in control of said motor, control means for closing the first circuit to cause operation of said motor, a second circuit in control of said motor, periodically operated control means for periodically closing the second circuit to cause periodic operation of said motor including constantly operated cam means, means for adjusting the cam means to increase or decrease the riod of operation of the motor and means for adjusting the cam means to increase or decrease the number of periods of operation of the motor within a given time interval without varying the period ofoperation thereof.

26. In a control system, the combination of, a, motor, a .first circuit in control of said motor,

control means for closing the first circuit to cause I operation of said motor, a second circuit in control of said motor, periodically operated control means for periodically closing the second circuit to cause periodic operation of said motor including a pair of cams and means for constantly rotating said cams, means for adjusting said cams with respect to each other for varying the period of operation of the motor, and means for adjusting said cams to vary the number of periods of operation of the motor within a given time interval without varying the period of operation thereof.

27. In a control system, the combination of, a motor, a first circuit in control of said motor, control means for closing the first circuit to cause operation of said motor, a second circuitin control of said motor, periodically operated controlmeans for periodically closing the second circuit to cause periodic operation of said motor including constantly operated cam means and means for adjusting said cam means to vary the number of periods of operation of said motor by 1 given time interval without varying the period said periodically operated control means within a given time interval without varying the period of operation thereof.

28. In a control system, the combination of, a motor, means including a first circuit in control of said motor, control means for closing the first circuit to cause operation of said motor, a second circuit in control of said motor, periodically operated control means for periodically closing the second circuit to cause periodic operation of said motor including constantly operated cam means, means for adjusting the cam means to increase or decrease the period of operation of the motor, means for adjusting the cam means to increase or decrease the number of periods of operation of the motor within a of operation thereof and means controlled by the means including the first circuit and operated by closure of the first circuit to preclude closing of the second circuit for an appreciable period subsequent to opening of the first circuit.

29. In a control system, the combination of, a motor, means including a first circuit in control of said motor, control means for closing the first circuit to cause operation of said motor, a second circuit in control of said motor, periodically operated control means for periodically closing the second circuit to cause periodic operation of said motor including constantly operated cam means, means for adjusting said cam means to vary the number of periods of operation of said motor by said periodically operated control means within a given time interval without varying the period of operation thereof, and means controlled by said means including the first circuit and operated by closure of said first circuit to preclude closing of the second circuit for an appreciable period subsequent to opening of said first circuit by said first mentioned control means.

30. In a control system, the combination of a motor, means including a first circuit in control of said motor, control means for closing the first circuit to cause operation of said motor, a second circuit in control of said motor, periodically operated control means for periodically closing the second circuit to cause periodic operation of said motor including continuously operated cam means, means for adjusting the cam means to vary the duration of the period of operation of the motor, and means controlled by the means including the first circuit and operated by closure of the first circuit to preclude closing of the second circuit for an appreciable period subsequent to opening of the first circuit.

31. A stoker control system comprising, in combination, a plurality of circuits, condition responsive means to operate said stoker through one of said circuits, time controlled means to operate said stoker through another of said circuits, and means to prevent continued operation of said stoker through said circuit of said condition responsive means after original energization of said stoker through said circuit of said time controlled means in the absence of condition change suflicient to cause energization of the stoker by said condition responsive means, said means including a make and break contact in the circuit controlled by said condition responsive means, the arrangement being such that said contact is opened by said time controlled means prior to closing of said time controlled circuit and reclosed by said time controlled means subsequent to reopening of said time controlled circuit.

32. In a heating system for a space having heating means for the space and a stoker for firing the heating means, the combination of, a relay having a control winding, a maintaining switch'and a load switch for the stoker, the maintaining switch and the load switch being closed when the control winding is energized, a space thermostat having a pair of switches that are sequentially closed upon a decrease in space temperature, means for completing a starting circuit through the control winding of the relay and the last to close switch of the thermostat to close the maintaining switch and the load switch for starting. operation of the stoker, means for completing a maintaining circuit through the control winding of the relay, the first to close switch of the thermostat and the maintaining switch to maintain the load switch closed and the stoker in operation until the first to close switch of the thermostat is opened, a timer, a first switch periodically opened and closed by the timer, a normally closed second switch operated by the timer and maintained momentarily opened following opening of the first switch, and means for completing a circuit through the control winding of the relay and the periodically operated first switch to close periodically the maintaining switch and the load switch to operate periodically the stoker independently of the thermostat, said second timer operated switch being included 'in the maintaining circuit to prevent continued operation of the stoker following a timed operation when only the first to make switch of the thermostat is closed.

ELMER K. SCOGGIN. 

